Positioning abrasive discs for dressing



\ April 21, 1959 RE. pme

POSITIONING ABRASIVE DISCS FOR DRESSING 2 Sheets-Sheet: 1

filed Oct. 18, 1957 INVENTOR RALPH 5- PRICE TTORNEY April 21, 1959 R. E. PRICE 2,882,651

r POSITIONING ABRASIVE DISCS FOR DRESSING Filed Oct. -l8; 1957 2 Sheets-Sheet 2 INVENTOR RALPH E- PRICE BY I fixkm TTORNEY I United States Patent 2,882,651 POSITIONING ABRASIVE DISCS FOR DRESSING Ralph E. Price, Waynesboro, Pa., assignor to Gardner Machine Company, Beloit, Wis.

Application October 18, 1957, Serial No. 691,027 Claims. (Cl. 51-118) This invention relates to surface grinding machines of the type known as disc grinders, particularly double disc grinders in which parallel surfaces of a workpiece may be ground at the same time.

The dressing operation in this type of machine is efiected by a pair of diamonds or other type of dressing tool usually mounted in a single supporting member and passed across the operative surfaces of a grinding disc to dress both discs at the same time. In order to perform such'a dressing operation automatically, the diamonds must be spaced by an exact amount, bearing a known relation to the space between the surfaces of the work to be ground. The discs must then be retracted accurately to a position in which the dressing operation may be initiated without further adjustment of the discs. The discs should be advanced toward grinding position by'a predetermined increment for each pass of the dressing tool in order to compensate for the amount of abrasive removed from the operative surface of the disc. Correction for wear is inherent in the spacing of the dressing tools.

After the dressing operation, the discs must be returned accurately to a position in which they are both at equal distances from the center of the piece to be ground and spaced apart by a distance which is exactly the dimension of the workpiece to be ground. If there were no lost motion between the moving parts of the feed mechanism and all the parts were perfectly rigid, compensation for wear and dressing would be sutficient to return the discs to the desired position. The separating of the discs for dressing and returning them to grinding position causes changes in the relation between the various parts of the feeding mechanism and the wheel support both in the form of lost motion and in the form of stresses set up in the various parts of the feeding mechanism.

It is therefore an object of this invention to provide means whereby the discs of a double disc grinder may be separated, dressed and adjusted to compensate for wear and dressing and returned to grinding position with the operative faces of the discs spaced by a distance equal to the finished dimension between the surfaces to be ground.

Another object is to provide means for compensating for lost motion and for relieving stresses in the feed mechanism.

Figure 1 is a front elevation of the right hand wheel support of a double disc grinder.

Figure 2 is a partial end elevation of said support.

Figure 3 is a hydraulic and electric diagram.

Numeral indicates the bed of a disc grinder. 11 is an intermediate slide in which the feed mechanism is mounted. 12 is a spindle housing slidably mounted for longitudinal movement on said intermediate slide 11. A spindle 15 rotatably mounted in said spindle housing 12 is driven through suitable connections by a motor 16 mounted on said spindle housing 12. A grinding wheel or disc 20 is mounted on a plate 21 attached to spindle 15. The means for moving disc 20 toward and from operative position includes a pair of hydraulic motors consisting of cylinders 30 and 31, having pistons 32 and 33 slidably mounted in said respective cylinders. Pistons 2,882,651 Patented Apr. 21, 1959 32 and 33 are connected through piston rods 34 and 35 to a portion 36 of spindle housing 12.

The grinding position and the dressing position of the spindle housing 12 are determined by an inner feed nut 40 and an outer feed nut 41 on a feed screw 42. A yoke member 50 extending downwardly from spindle housing 12 has an opening 51 through which the feed screw 42 passes. The longitudinal movement of spindle housing 12 is determined by the engagement of yoke member 50 with one or the other nut 40 or 41. Each of said nuts has a plurality of peripherally spaced notches 60. A key member 61 removably attached to yoke member 50 passes through the aligned notches 60 in both nuts 40 and 41 to prevent rotation of said nuts once they have been adjusted. Two limit switches 10LS and 12LS are attached to yoke member 50 by means of bracket 55. Corresponding switches 11LS and 13LS, respectively, on the opposite spindle housing 12 are mounted in the same manner.

Means for turning feed screw 42 consists of a worm wheel 70 on the end of feed screw 42 and a worm gear 71 in operative engagement with said worm Wheel 70, said worm gear 71 being mounted on shaft 72. Shaft 72 may be rotated by means of a hand wheel 73 or by a pawl and ratchet mechanism consisting of a ratchet wheel 75 and a pawl 76. Pawl 76 ispivotally attached to an arm 77 also mounted on shaft 72. Ann 77 and pawl 76 may be actuated by a piston 80 in cylinder 81, and having a piston rod 82 attached to arm 77 and pawl 76.

Operation Machine start switch closes to energize lCR. 1CR3 provides a holding circuit and 1CR1 provides a circuit for the entire machine.

Dresser start switch is closed to energize 7CR. 7CR energizes valve solenoid C which shifts valve 1 to direct fluid under pressure to the rod ends of head cylinders 30 and 31.

As soon as the heads move out, 10LS and 11LS are released. 10LSB and 11LS-B complete a circuit to energize 17CR. 17CR4 and 17CR5 complete a circuit to energize valve solenoid D. The valve directs fluid under pressure to the head ends of cylinders 101, moving pistons upwardly and turning ratchet shields 102 in the direction to expose a greater number of teeth to pawl action on ratchet wheels 75 for dressing.

17CR2, along with normally closed 7LSB and normally closed 8LSB, provides a holding circuit for 17CR.

When the heads or spindle housings 12 reach dressing position, normally open 12LS and 13LS are closed to complete a circuit through normally closed 11CR3 and normally closed 12CR3 to energize 14CR. 14CR1 and 14CR2 complete a circuit to energize 18CR and 19CR respectively. 18CR3 and 18CR4 complete a circuit to energize valve solenoid A, and 19CR3 and 19CR4 complete a circuit to energize valve solenoid B.

Valve solenoids A and B shift the valves to the right to direct fluid under pressure to the head ends of ratchet cylinders 81, moving ratchet pistons 80 upwardly to cause pawls 76 to engage feed ratchets 75 which, in turn, turn feed screws 42 to advance nuts 41 to force the advance of discs 20 against the pressure in the rod ends of cylinenergize dresser relay R. A holding circuit around 7LS-A and 8LSA is provided through 11CR1 to hold 11CR.

11CR4 and 11CR5 complete a circuit to energize valve solenoid F, shifting the valve to the left and directing fluid under. pressure...to.the rodend ofi cylinder. 90, moving. piston 91 downwardly and swinging diamond holder 92 in a clockwise direction to make the first pass across the disc 20a Normally closed 11CR3 opens to deenergize 14CR which, in turn, .deenergizes' 18CR'and 190R and valveisolenoids-A andB which. are shifted by their springs A-1'.'and:B1 'to.:the' left to retract pawls 76.

Atthe end of the first. inward dressing stroke, 9LS is released; 9LS-A opens the circuit to 11CR, closing normally closed 11CR2 to complete a circuit from 9LS B. to 12CR. 11CR1, inthe same circuit, is opened andlZCR remains deenergized. Normally closed 11CR3 and normally-closed 12CR3 complete a circuit through LSA, 11LS-A and 17CR3 to energize. 14CR.

14CR1 and 14CR2. act through 18CR and 19CR to again energize valve solenoids A and B, and provide a feed impulse to the feedratchets of spindle housings 12. 11CR4. andllCRS open to deenergize valve solenoid F.

Normally closed 11CR2 closes to. energize 120R. 12CR6 and 12CR7 energize valve solenoid G which shifts the valve to-the left to. directfluid to the head end of cylinder 90 to rotate or swing diamond holder 92 in encounter-clockwisedirection to move the diamond to the out or start position. At the end of this movement, the counter ICTR counts out for one cycle or for a predetermined number of cycles; 1CTR2 closes, energizingglSCR. 13CR2 keeps IZCR energized until ICTR counts out. When counted out, the diamond holder 92 moves to close 4LS-A. It also closes 9LS--A and opens 9LS'B. Closing 4LS-A energizes 9CR. 9CR4 closes to energize 100R. 10CR2 and 10CR3 energize valvesolenoid E. The valve is shifted to the right to direct fluid under pressure. to the head ends of cylinders 30 and 31 to return the heads to grinding position, andIZLS-and 13LS open.

When heads reach grinding position and lugs 50 contact nuts 40, 10LSA and liLS-A close, and 10LSB and'11LS-B'- open. 17CR is held through 7LS--B, 8LS-B and 17CR2. 10LSA, 11LSA and 17CR3 complete a circuit through normally closed 11CR3 and normally closed 12CR3 to energize 14CR for a final feed impulse to compensate for the backlash, windup and other changes which take place in a feed mechanism. The amount of this feed increment is equal to the dressing feed increment, and is predetermined and adjusted to exceed the amount ofithe hand wheel rotation required to correct the setting of the feed mechanism. 7LS-B and SLS-B open during the final feed adjustment and deenergize 17CR and valve solenoid D.

Valve solenoid D and the feed control valve are shifted to the left by the valve spring to direct fluid under pressure to the rod ends of cylinders 101 to shift ratchet shields 102 to compensating'feed position for grind size control.

Iclaim:

l. A grinding machine having annularly opposed grinding discs: rotatably mounted thereon, means for adjusting'said discs toward and from one another including a feed screw and nut, means for efiecting a rapid positioning movement of said discs toward and from one another, a dressing device comprising a diamond holder having spaced oppositely positioned diamonds thereon, the spacing of said diamonds being greater than the spacingbetween the grinding discs during a grinding operation, means for actuating said rapid positioning means to separatesaid discs for a dressing operation, means responsive to said rapid positioning movement to advance said adjusting means by a predetermined amount, means actuated by said adjusting means'to actuate said dressing device to make a dressing pass across said oppo's'ed discs, means operable at-the end of said dressing pass-to automatically actuate said feed adjusting mechanism to advance said discs to compensate for the amount to be dressed by the diamonds on the return pass of the dressing-device across the wheel, means actuated after a predetermined dressing operation to, actuate saidrapid positioning means to return said discs to said operative position, and control means to effect a final operation of said feed adjusting mechanism to compensate for strain and backlash in the feed mechanism during the dressing operation.

2. In a grinding machine having axially opposed grinding discs rotatably mounted thereon, means for adjusting said discs toward and from one another including a feed screw and nut, means for effecting a rapid positioning movement of said discs toward and from one another, a dressing device comprising a diamond holder having spaced oppositely positioned diamonds thereon, means to actuate said dressing device to make a dressing pass across said opposed discs, means responsive to movement of said dresser to automatically actuate said feed adjusting mechanism to advance said discs to compensatefor the amount to be dressed by the diamonds on thereturn pass of the dressing device across the wheel, means including a counting device to actuate said rapid positioning means to return said discs to said operative position after said dressing operation, and means responsive to return movement of said discs to effect a finaloperation of said feed adjusting mechanism to compensate for changes occurring in the feed mechanism as a result of the movement to and from dressing position.

3. In a grinding machine having annularly opposedgrinding discs rotatably mounted thereon, means for adjusting said discs toward and from one another including, a feed mechanism, means for effecting a rapid positioning movement of said discs toward and from one another, means for actuating said rapid positioning means to separate said discs for a dressing operation, means to eifect said rapid positioning means to return said discs to operative position after said dressing operation, and meansoperable upon return of said discs to said operative position to efiect operation of said feed adjusting mechanism to compensate for changes occurring in said feed mechanism as a result of said movement to and from dressing position.

4. In a disc grinder, a bed, a wheel supporting member slidably mounted on said bed, a grinding wheel or disc rotatably mounted in said wheel supporting member, means for efiecting an axial positioning movement of said disc including a hydraulic motor, means for determining the extent of movement of said disc by said motor including a feed screw, a pair of feed nuts mounted in axially spaced relation on said feed screw, an abutment on said wheel supporting member extending into the space between said feed nuts, and means for adjusting: said feed screw to change the axial position of said feed nuts and therefore the zone of movement of said wheel supporting member.

5. In a disc grinder, a bed, a wheel supporting member slidably mounted on said bed, a grinding wheel or disc rotatably mounted in said wheel supporting member, means for eifecting an axial positioning movement of said disc including a hydraulic motor, means for determining the extent of movement of said disc by said motor including a feed screw, a pair of feed nuts mounted in axially spaced relation on said feed screw, an abutment on said wheel supporting member extending into the space between said feed nuts, and means for eifecting arelative adjustment between said feed screw and said feednuts to change the axial position of said feed nuts and therefore the zone of movement of said wheel supporting member.

References Cited in the file of this patent UNITED STATES PATENTS 2,033,922 Cole Mar. 17, 1936 2,082,736 Indge June 1, 1937 2,285,717" Indge June 9, 1942 

